Great Falls Weather in May
Average highs run from 63°F on May 1 to 70°F on May 31, and lows from 37°F to 46°F. Normal precipitation for the month is 2.66 in over about 11 wet days.
May day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
May at a glance
- Average high
- 67°F
- Average low
- 42°F
- Precipitation
- 2.66 in
- Snowfall
- 1.9 in
- Record high
- 93°FMay 21, 1980
- Record low
- 12°FMay 1, 2009
- Chance of a freeze
- 71%
- Daylight
- 14 h 29 min to 15 h 41 min
- Cloud cover
- 67%
- Humidity
- 59%
- Dew point
- 36°F
- Wind
- 8.7 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| May 1 | 63°F | 37°F | 83°F 2000 | 12°F 2009 | 30% | 10% |
| May 2 | 64°F | 38°F | 86°F 1985 | 16°F 1954 | 30% | 9% |
| May 3 | 64°F | 38°F | 84°F 1966 | 19°F 1967 | 30% | 9% |
| May 4 | 64°F | 38°F | 85°F 1966 | 23°F 1996 | 31% | 9% |
| May 5 | 65°F | 39°F | 86°F 2017 | 25°F 2026 | 31% | 8% |
| May 6 | 65°F | 39°F | 87°F 1966 | 23°F 2026 | 31% | 8% |
| May 7 | 65°F | 39°F | 86°F 1985 | 26°F 2001 | 31% | 8% |
| May 8 | 65°F | 40°F | 88°F 1987 | 21°F 1999 | 32% | 7% |
| May 9 | 66°F | 40°F | 85°F 1987 | 24°F 1990 | 32% | 7% |
| May 10 | 66°F | 40°F | 86°F 1940 | 21°F 2004 | 32% | 7% |
| May 11 | 66°F | 40°F | 88°F 1960 | 23°F 1983 | 33% | 7% |
| May 12 | 66°F | 41°F | 90°F 2001 | 22°F 1943 | 33% | 6% |
| May 13 | 67°F | 41°F | 89°F 2026 | 20°F 2004 | 33% | 6% |
| May 14 | 67°F | 41°F | 84°F 1939 | 26°F 2004 | 34% | 6% |
| May 15 | 67°F | 42°F | 87°F 1987 | 30°F 1955 | 34% | 5% |
| May 16 | 67°F | 42°F | 92°F 1988 | 30°F 1942 | 35% | 5% |
| May 17 | 67°F | 42°F | 87°F 2006 | 26°F 2003 | 35% | 5% |
| May 18 | 68°F | 43°F | 90°F 2006 | 27°F 1977 | 36% | 5% |
| May 19 | 68°F | 43°F | 89°F 1964 | 30°F 1997 | 36% | 5% |
| May 20 | 68°F | 43°F | 88°F 1958 | 26°F 2021 | 37% | 4% |
| May 21 | 68°F | 44°F | 93°F 1980 | 24°F 2022 | 37% | 4% |
| May 22 | 68°F | 44°F | 88°F 1980 | 26°F 2021 | 38% | 4% |
| May 23 | 69°F | 44°F | 88°F 1988 | 30°F 1949 | 38% | 4% |
| May 24 | 69°F | 44°F | 88°F 1941 | 30°F 1995 | 38% | 4% |
| May 25 | 69°F | 45°F | 86°F 1940 | 31°F 2012 | 38% | 3% |
| May 26 | 69°F | 45°F | 88°F 1966 | 30°F 1975 | 39% | 3% |
| May 27 | 69°F | 45°F | 87°F 1966 | 29°F 1995 | 39% | 3% |
| May 28 | 70°F | 45°F | 90°F 1958 | 27°F 1947 | 39% | 3% |
| May 29 | 70°F | 46°F | 89°F 1984 | 32°F 1951 | 39% | 3% |
| May 30 | 70°F | 46°F | 89°F 1986 | 33°F 1951 | 39% | 3% |
| May 31 | 70°F | 46°F | 90°F 1972 | 30°F 1982 | 39% | 2% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (MDT).
- May 1
- sunrise 6:08 AM, sunset 8:37 PM
- May 31
- sunrise 5:33 AM, sunset 9:14 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00243749 (Great Falls 16ST), public domain. Records: NOAA GHCN-Daily, station USW00024143, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.